The present invention is referred to a tank suitable to contain high pressure fluids, typically for compressed natural gas (CNG) for automotive purposes, which tank has a bombé disc shape particularly suitable for on board vehicles installation.
It is known that the current production of high pressure compressed natural gas tanks exclusively consists of the so-called “cylinders”, steel made by different manufacturing processes.
These cylinders present a cylindrical shape, mainly lengthened and tapered at the two ends.
The use of the above mentioned type of cylinders in the automotive field with compressed natural gas, is till today rather limited, and this especially because of the weight and the dimensions of the cylinders themselves, these characteristics being absolutely necessary to have a satisfying route autonomy, before the subsequent refuelling.
The attempts to reduce weight and dimensions of the cylinders themselves are anyway contrasted by the necessity to comply with the actual regulations in force which are inspired to absolutely safety criterions.
During the last years it has been started the production of CNG high pressure cylinders for automotive purposes which include and internal core (said also liner) in different materials and covered by composite materials soaked with appropriates resins.
The function of the coating is to supply to the cylinder the necessary resistance to support the high pressures of the gas, which cannot be supported by the inside core, also of reduced thickness.
For safety reasons, the main international rules, referred to compressed natural gas cylinders for automotive purposes (CNG automotive purposes), such as ISO11439, NGV2, R110, basically identify four types of containers, respectively named:                TYPE 1: cylinder fully made of steel;        TYPE 2: liner made of steel or aluminium reinforced by fiber filament in its cylindrical part;        TYPE 3: steel or aluminium liner reinforced by fiber filament on all its surface;        TYPE 4: cylinders fully made by composite material;        TYPE 5: other possible types of manufacture, not included in types from 1 to 4.        